1. Field of the Invention
The present invention is directed to a fuel processor, and, more particularly, to a control system for use in a fuel processor.
2. Description of the Related Art
There are numerous uses for pure hydrogen or hydrogen-enriched gas streams. For instance, fuel cells—a promising alternative energy source—typically employ hydrogen as a fuel for generating power. Many industrial processes also employ hydrogen or hydrogen-enriched gas streams in a variety of fields for the manufacture and production of a wide assortment of end products. However, pure hydrogen is not available as a natural resource in a form that can be readily exploited. As an example, natural gas, a hydrocarbon-based fuel, is frequently found in large subterranean deposits that can be easily accessed and transported once tapped. Nature does not provide such deposits of hydrogen.
One way to overcome this difficulty is the use of “fuel processors” or “reformers” to convert hydrocarbon-based fuels to a hydrogen rich gas stream which can be used as a feed for fuel cells. Hydrocarbon-based fuels, such as natural gas, liquid petroleum gas (“LPG”), gasoline, and diesel, require conversion for use as fuel for most fuel cells. Current art uses multi-step processes combining an initial conversion process with several clean-up processes. The initial process is most often steam reforming (“SR”), autothermal reforming (“ATR”), catalytic partial oxidation (“CPOX”), or non-catalytic partial oxidation (“POX”). The clean-up processes are usually comprised of a combination of desulfurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation. Alternative processes include hydrogen selective membrane reactors and filters.
More particularly, the ATR performs a water-gas shift reaction that reduces CO concentration and increases H2 production rate. This reaction is exothermal and sensitive to the temperature. Shift reaction temperature control is therefore a significant element for continuously making stable, low CO concentration and high H2 yield reformate. And, better temperature control provides a more consistent, higher quality end product.
The ATR performs the water-gas shift reaction in what is called a “shift bed.” The water gas shift reaction, which reduces CO concentration and increases H2 production rate. This reaction is exothermal and sensitive to the temperature, therefore preheating and water cooling are used to maintain the temperature of the shift bed within an optimum reaction temperature range. As a result, condensation sometimes occurs on the shift catalyst of the shift bed, thus decreasing its level of activity with time. This decreasing level of activity negatively impacts the performance of the ATR.
The shift bed is therefore periodically subjected to a process called “regeneration” to revitalize the shift bed. Regeneration re-activates the catalyst to its starting level of performance. Careful control of temperature across the catalyst bed during the regeneration is necessary yet difficult to control. The temperature is also controlled to prevent damage to other types of catalysts found in the ATR such as ZnO, POx and ATR. Currently, this control is implemented manually. The task is tedious and arduous, and is compounded by the relatively long time that the process takes to complete.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.